Drilling a curved hole

Abstract

Drilling apparatus for attachment to a rotary motor includes a flexible shaft confined in an elongated tubular sheath. The sheath is formed from a semi-rigid material which is bendable to a desired curvature, at the use site to select the curvature of the drilled hole, and which is rigid enough to retain that curvature in use. A drilling bit is fixed to one end of the flexible shaft, and includes a shank coacting with the distal end of the sheath to rotationally guide the drilling bit. The flexible shaft projects from the sheath at the proximal end so that both components may be secured to a drilling motor which is manipulated to guide the sheath while rotating the cutting bit. The sheath may remain in the drilled hole temporarily as a liner to guide the passage therethrough of a relatively stiff wire or other filamentary member.

What is claimed is: 
     
       1. An attachment for a rotary motor for drilling curved holes in bone tissue comprising an elongated flexible drive shaft havaing a proximal end configured to be coupled to a rotary drive motor, and having a rotary drilling tool fixed to the distal end of the drive shaft;   a semi-rigid tubular sheath, intentionally manually deformable to a selected curvature by the user, enclosing and guiding said flexible drive shaft and adapted to be non-rotatably coupled at one end to said rotary drive motor;   said drilling tool having an outer diameter slightly larger than that of said sheath; and said shaft proximal end being dimensioned to pass through said sheath to enable removal of said drilling tool and shaft from said sheath.   
     
     
       2. An attachment as set forth in claim 1 further comprising said sheath being formable by the user to a selected radius of curvature, and having a stiffness sufficient to maintain the selected radius of curvature during the operation thereof.   
     
     
       3. An attachment as set forth in claim 2 further comprising said shaft having an outer diameter significantly smaller than the inner diameter of said sheath to provide for free rotatation of said shaft within said sheath.   
     
     
       4. An attachment as set forth in claim 1 further comprising said drilling tool having a journal shank nonrotatably fixed to said flexible shaft; said shank having an outer diameter only slightly smaller than the inner diameter of said sheath whereby said sheath provides bearing support for said journal shank.   
     
     
       5. An attachment as set forth in claim 4 further comprising said flexible shaft having an outer diameter smaller than that of said journal shank, to provide clearance between said shaft and said enclosing sheath.   
     
     
       6. A method for drilling a curved hold in bone tissue comprising the steps driving a rotary drilling tool by means of a flexible shaft having said tool fixed to its distal end;   enclosing said flexible shaft in a tubular guiding sheath intentionally formable by the user to a selected curvature;   configuring said sheath to have an outer diameter smaller than that of said drilling tool;   advancing said drilling tool through the material to be drilled by means of said sheath while rotatably driving said drilling tool.   
     
     
       7. A method as set forth in claim 6 including the step, prior to advancing said drilling tool, of manually forming said sheath to a desired curvature.   
     
     
       8. A method as set forth in claim 6 including the step of withdrawing said drilling tool and attached flexible shaft from said sheath, whereby said sheath provides a liner guide for the drilled hole.   
     
     
       9. A method as set forth in claim 8 including the steps of threading a filamentary member through said sheath within said hole; and   withdrawing said sheath from said hole, leaving said filamentary member in place.   
     
     
       10. A method as set forth in claim 8 including the step of withdrawing said drilling tool and attached flexible shaft from said sheath, while said sheath remains within the drilled hole whereby said sheath provides said liner guide.   
     
     
       11. A method as set forth in claim 6 including the step of journaling said drilling tool within the distal end of said sheath.   
     
     
       12. A method as set forth in claim 6 including the steps of advancing said drilling tool through said material in one direction to complete a through curved hole; and   withdrawing said drilling tool and attached flexible shaft from said sheath while said sheath remains in said hole, whereby said sheath provides a liner guide for said drilled hole.   
     
     
       13. A method as set forth in claim 12 including the steps of threading a filamentary member through said sheath within said hole; and   withdrawing said sheath from said hole, leaving said filamentary member in place.   
     
     
       14. A method as set forth in claim 6 including the step, prior to advancing said drilling tool, of forming said sheath to a selected configuration at the use site.   
     
     
       15. A method as set forth in claim 14 including the step of said forming of said sheath including bending the distal end thereof to a selected radius of curvature.   
     
     
       16. A method as set forth in claim 15 including the step of said forming of said sheath including the bending of said sheath to orient the curved distal end in a selected plane relative to the linear proximal end thereof.